github.com/tcnksm/go@v0.0.0-20141208075154-439b32936367/src/runtime/print1.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import "unsafe"

// The compiler knows that a print of a value of this type
// should use printhex instead of printuint (decimal).
type hex uint64

func bytes(s string) (ret []byte) {
	rp := (*slice)(unsafe.Pointer(&ret))
	sp := (*_string)(noescape(unsafe.Pointer(&s)))
	rp.array = sp.str
	rp.len = uint(sp.len)
	rp.cap = uint(sp.len)
	return
}

// printf is only called from C code. It has no type information for the args,
// but C stacks are ignored by the garbage collector anyway, so having
// type information would not add anything.
//go:nosplit
func printf(s *byte) {
	vprintf(gostringnocopy(s), add(unsafe.Pointer(&s), unsafe.Sizeof(s)))
}

// sprintf is only called from C code. It has no type information for the args,
// but C stacks are ignored by the garbage collector anyway, so having
// type information would not add anything.
//go:nosplit
func snprintf(dst *byte, n int32, s *byte) {
	buf := (*[1 << 30]byte)(unsafe.Pointer(dst))[0:n:n]

	gp := getg()
	gp.writebuf = buf[0:0 : n-1] // leave room for NUL, this is called from C
	vprintf(gostringnocopy(s), add(unsafe.Pointer(&s), unsafe.Sizeof(s)))
	buf[len(gp.writebuf)] = '\x00'
	gp.writebuf = nil
}

var debuglock mutex

// The compiler emits calls to printlock and printunlock around
// the multiple calls that implement a single Go print or println
// statement. Some of the print helpers (printsp, for example)
// call print recursively. There is also the problem of a crash
// happening during the print routines and needing to acquire
// the print lock to print information about the crash.
// For both these reasons, let a thread acquire the printlock 'recursively'.

func printlock() {
	mp := getg().m
	mp.printlock++
	if mp.printlock == 1 {
		lock(&debuglock)
	}
}

func printunlock() {
	mp := getg().m
	mp.printlock--
	if mp.printlock == 0 {
		unlock(&debuglock)
	}
}

// write to goroutine-local buffer if diverting output,
// or else standard error.
func gwrite(b []byte) {
	if len(b) == 0 {
		return
	}
	gp := getg()
	if gp == nil || gp.writebuf == nil {
		write(2, unsafe.Pointer(&b[0]), int32(len(b)))
		return
	}

	n := copy(gp.writebuf[len(gp.writebuf):cap(gp.writebuf)], b)
	gp.writebuf = gp.writebuf[:len(gp.writebuf)+n]
}

func prints(s *byte) {
	b := (*[1 << 30]byte)(unsafe.Pointer(s))
	for i := 0; ; i++ {
		if b[i] == 0 {
			gwrite(b[:i])
			return
		}
	}
}

func printsp() {
	print(" ")
}

func printnl() {
	print("\n")
}

// Very simple printf.  Only for debugging prints.
// Do not add to this without checking with Rob.
func vprintf(str string, arg unsafe.Pointer) {
	printlock()

	s := bytes(str)
	start := 0
	i := 0
	for ; i < len(s); i++ {
		if s[i] != '%' {
			continue
		}
		if i > start {
			gwrite(s[start:i])
		}
		if i++; i >= len(s) {
			break
		}
		var siz uintptr
		switch s[i] {
		case 't', 'c':
			siz = 1
		case 'd', 'x': // 32-bit
			arg = roundup(arg, 4)
			siz = 4
		case 'D', 'U', 'X', 'f': // 64-bit
			arg = roundup(arg, unsafe.Sizeof(uintreg(0)))
			siz = 8
		case 'C':
			arg = roundup(arg, unsafe.Sizeof(uintreg(0)))
			siz = 16
		case 'p', 's': // pointer-sized
			arg = roundup(arg, unsafe.Sizeof(uintptr(0)))
			siz = unsafe.Sizeof(uintptr(0))
		case 'S': // pointer-aligned but bigger
			arg = roundup(arg, unsafe.Sizeof(uintptr(0)))
			siz = unsafe.Sizeof(string(""))
		case 'a': // pointer-aligned but bigger
			arg = roundup(arg, unsafe.Sizeof(uintptr(0)))
			siz = unsafe.Sizeof([]byte{})
		case 'i', 'e': // pointer-aligned but bigger
			arg = roundup(arg, unsafe.Sizeof(uintptr(0)))
			siz = unsafe.Sizeof(interface{}(nil))
		}
		switch s[i] {
		case 'a':
			printslice(*(*[]byte)(arg))
		case 'c':
			printbyte(*(*byte)(arg))
		case 'd':
			printint(int64(*(*int32)(arg)))
		case 'D':
			printint(int64(*(*int64)(arg)))
		case 'e':
			printeface(*(*interface{})(arg))
		case 'f':
			printfloat(*(*float64)(arg))
		case 'C':
			printcomplex(*(*complex128)(arg))
		case 'i':
			printiface(*(*fInterface)(arg))
		case 'p':
			printpointer(*(*unsafe.Pointer)(arg))
		case 's':
			prints(*(**byte)(arg))
		case 'S':
			printstring(*(*string)(arg))
		case 't':
			printbool(*(*bool)(arg))
		case 'U':
			printuint(*(*uint64)(arg))
		case 'x':
			printhex(uint64(*(*uint32)(arg)))
		case 'X':
			printhex(*(*uint64)(arg))
		}
		arg = add(arg, siz)
		start = i + 1
	}
	if start < i {
		gwrite(s[start:i])
	}

	printunlock()
}

func printpc(p unsafe.Pointer) {
	print("PC=", hex(uintptr(p)))
}

func printbool(v bool) {
	if v {
		print("true")
	} else {
		print("false")
	}
}

func printbyte(c byte) {
	gwrite((*[1]byte)(unsafe.Pointer(&c))[:])
}

func printfloat(v float64) {
	switch {
	case v != v:
		print("NaN")
		return
	case v+v == v && v > 0:
		print("+Inf")
		return
	case v+v == v && v < 0:
		print("-Inf")
		return
	}

	const n = 7 // digits printed
	var buf [n + 7]byte
	buf[0] = '+'
	e := 0 // exp
	if v == 0 {
		if 1/v < 0 {
			buf[0] = '-'
		}
	} else {
		if v < 0 {
			v = -v
			buf[0] = '-'
		}

		// normalize
		for v >= 10 {
			e++
			v /= 10
		}
		for v < 1 {
			e--
			v *= 10
		}

		// round
		h := 5.0
		for i := 0; i < n; i++ {
			h /= 10
		}
		v += h
		if v >= 10 {
			e++
			v /= 10
		}
	}

	// format +d.dddd+edd
	for i := 0; i < n; i++ {
		s := int(v)
		buf[i+2] = byte(s + '0')
		v -= float64(s)
		v *= 10
	}
	buf[1] = buf[2]
	buf[2] = '.'

	buf[n+2] = 'e'
	buf[n+3] = '+'
	if e < 0 {
		e = -e
		buf[n+3] = '-'
	}

	buf[n+4] = byte(e/100) + '0'
	buf[n+5] = byte(e/10)%10 + '0'
	buf[n+6] = byte(e%10) + '0'
	gwrite(buf[:])
}

func printcomplex(c complex128) {
	print("(", real(c), imag(c), "i)")
}

func printuint(v uint64) {
	var buf [100]byte
	i := len(buf)
	for i--; i > 0; i-- {
		buf[i] = byte(v%10 + '0')
		if v < 10 {
			break
		}
		v /= 10
	}
	gwrite(buf[i:])
}

func printint(v int64) {
	if v < 0 {
		print("-")
		v = -v
	}
	printuint(uint64(v))
}

func printhex(v uint64) {
	const dig = "0123456789abcdef"
	var buf [100]byte
	i := len(buf)
	for i--; i > 0; i-- {
		buf[i] = dig[v%16]
		if v < 16 {
			break
		}
		v /= 16
	}
	i--
	buf[i] = 'x'
	i--
	buf[i] = '0'
	gwrite(buf[i:])
}

func printpointer(p unsafe.Pointer) {
	printhex(uint64(uintptr(p)))
}

func printstring(s string) {
	if uintptr(len(s)) > maxstring {
		gwrite(bytes("[string too long]"))
		return
	}
	gwrite(bytes(s))
}

func printslice(s []byte) {
	sp := (*slice)(unsafe.Pointer(&s))
	print("[", len(s), "/", cap(s), "]")
	printpointer(unsafe.Pointer(sp.array))
}

func printeface(e interface{}) {
	ep := (*eface)(unsafe.Pointer(&e))
	print("(", ep._type, ",", ep.data, ")")
}

func printiface(i fInterface) {
	ip := (*iface)(unsafe.Pointer(&i))
	print("(", ip.tab, ",", ip.data, ")")
}